It’s more designed as a portable companion for PC players but it can also be a gateway to PC gaming. If money was a consideration then the answer would clearly be no, but since it isn’t then whatever buy and check it out. Something that PC/Deck gaming requires additionally is time because many games require troubleshooting and tweaking to work properly even the Verified ones. Not like console where the expectation is you press play and the game just works, already fully optimized for the platform.

CE:A has always been unstable even on Windows. Just play Classic graphics.

No. In your situation I would get a used LCD Deck + a cheap dock once everyone else dumps theirs on the second hand market to upgrade to OLED. There is almost no performance boost from the LCD model and your main use case (retro AAA) doesn’t involve portability, just couch gaming. You want the cheapest deal possible not the new&shiny otherwise you could have just built your own PC for less, or found used PS3/Xbox360. Option 2 would be to buy a Switch since the platform is seeing a surge of retro game releases but I’m not sure if those are the games your interested in. Also keep in mind just because a game is available on steam doesn’t mean it is compatible or runs well. This is biggest difference if your coming from console so make sure you do your research.